The thesis presents a cross-sectional study of the development of aspect marking in L2 Chinese by English native speakers. By using an acceptability judgement test, a storytelling task and a multiple-choice test, the study addresses three research questions: (1) What is the developmental sequence in the acquisition of four aspect markers in Chinese: the perfective markers guo and le, and the imperfective markers zai and zhe? (2) Does the development of the L2 Chinese aspectual system follow the predictions of the Aspect Hypothesis (AH), which has gained considerable support from research in L2 Indo-European languages? (3) What factors may account for the observed patterns of aspect marking in L2 Chinese? Moreover, since Chinese native speakers have also participated in the investigation, their data will corroborate and, more importantly, extend our knowledge of the Chinese aspectual system.

Results from the study show that although it may be possible to identify an order in the emergence of these aspect markers in the interlanguage, it is hard to conclude on a clear sequence in the acquisition of them. The L2 learners seem to experience specific and unique problems associated with each marker at different stages of the acquisition process. As for the associations between situation and viewpoint aspects, the patterns in the production data of the lower-intermediate (LI) learners, more or less, confirm the predictions of the AH about the early L2 tense and aspectual systems, although analyses of the acceptability judgement data show that the LI learners, incorrectly, accept the combination of the perfective marker VF-le with all situation types, indicating a strong influence from the learners' L1. With progress in learners' L2 proficiency, the interlanguage aspectual system does gradually approximate the target, though not along the path predicted by the AH. The patterns in the use of aspect markers by the upper-intermediate learners are more compatible with the predicted initial patterns in L2 acquisition, which are also the patterns found in the native speaker data. Based on these results, a proposal for rephrasing the AH has been made. With regard to the factors that may influence the L2 acquisition of Chinese aspect markers, the developmental data in the present study suggest that the restructuring of the aspectual system may result from an interaction of L1 interference, exposure to the input, and frequency and semantic complexity of the aspect markers in question.